Field of the Invention
The present invention relates to an endothermic catalytic dehydrogenation process.
Description of Related Art
The invention is concerned with an endothermic hydrocarbon process, particularly for catalytic dehydrogenation of paraffinic and other hydrocarbons such as propane dehydrogenation (reaction 1) or butane dehydrogenation (reaction 2) or i-butane dehydrogenation (reaction 3):C3H8C3H6+H2  (1)C4H10C4H6+2H2  (2)i−C4H10i−C4H8+H2  (3)
Dehydrogenation of hydrocarbons, in particular aliphatic hydrocarbons, to convert them into to their respective olefins is a well-known process. For example, the hydrocarbons propane, butane, isobutane, butenes and ethyl benzene are well known catalytically dehydrogenated to produce the respective propylene, butene, isobutene, butadiene and styrene. Dehydrogenation reactions are strongly endothermic and thus, an increase of the heat supply favours the olefin conversion.
One well known dehydrogenation process is the Houdry CATOFIN® process in which an aliphatic hydrocarbon is passed through a dehydrogenation catalyst bed where the hydrocarbon is dehydrogenated to the respective olefin, the olefin is flushed from the bed, the catalyst is regenerated and reduced, and the cycle is repeated (U.S. Pat. No. 2,419,997).
Some other well-known dehydrogenation technologies are Oleflex, Uhde-STAR and BASF-Linde process. Oleflex and CATOFIN technologies are adiabatic processes where the catalyst bed is heated directly. Uhde-STAR and BASF-Linde technologies are isothermal processes where the catalyst bed is heated indirectly.
CATOFIN propane dehydrogenation process is a cyclic process where during regeneration and reduction steps, heat is supplied to the catalyst bed and during dehydrogenation step catalyst bed cools down due to the endothermic dehydrogenation reaction. The upper section of the catalyst gets most of the heat during regeneration and reduction steps and supplies most of the heat to the reaction during the dehydrogenation reaction. On the other hand the heat consumed and supplied by the lower sections of the bed is quite low compared to the upper sections. Propylene production is normally controlled by equilibrium at the bottom section.
Another well-known process is CATADIENE® process in which butanes and butenes are dehydrogenated to produce butadiene.
Propane dehydrogenation reaction is an equilibrium limited reaction. One approach to shift the equilibrium towards the olefin product, such as propylene, can be decreasing the partial pressure of the alkane educt, such as propane. This can be achieved by adding a suitable diluent gas.
For example US 2004/0181107 A1 discloses the addition of carbon dioxide providing an in situ heat source for the reaction, decreases coke formation, enhances olefin selectivity and extends the dehydrogenation catalytic cycle. In addition an inert diluent, such as methane, or nitrogen may be added.
WO 2002/094750A1 proposes adding a diluent along with a source of halogen for the process of oxidative halogenations. US2004/0181104 A1 discloses the addition of an olefin to the dehydrogenation process to consume hydrogen and to shift equilibrium of dehydrogenation reaction.
US 2013/158327A1 suggests the addition of pure methane as inert diluent to the alkane feed for improving the yield of olefin in dehydrogenation process. The feed stream also contains hydrogen along with the alkane and inert diluent. The inert diluent increases the propylene yield of propane dehydrogenation process. However, a drawback of this approach is the availability and high cost of pure methane.
Thus, it would be of an advantageous to provide a process for improving conversion of a gas phase dehydrogenation process without having the above described drawbacks. It would be in particular of an advantageous to use a system which can improve the propylene yield of propane dehydrogenation reaction and is at the same time cost-efficient.